Pigeon pea

Leafhoppers or Jassids (Jacobiasca lybica)

Jassids (leafhoppers) have been reported to cause damage to pigeon peas in Kenya. These small (2.5 mm) green and very mobile insects occur on the upper and lower leaf surface. The adults fly or hop away when disturbed. Nymphs resemble adults, but have no wings, and run sideways when disturbed. The eggs are inserted in the veins on the underside of leaflets. Adults and nymphs feed by sucking on the leaflets. Attacked leaves become cup shaped and yellow at the edges. Heavy attacks result in the leaflets turning red-brown, with subsequent defoliation and stunting.

Cowpea seed beetle

They are the most common and widespread insect pests in storage. Adults are 2-3.5 mm long. They attack both pods in the field and seeds in storage. They attack nearly mature and dried pods. Infested stored seeds can be recognised by the round exit holes and the white eggs on the seed surface. Post-harvest losses are highly variable, but losses can be over 90%.

Root-knot nematodes (Meloidogyne incognita, M. javanica)

Affected plants are normally stunted and eventually wilt and die. The most characteristic symptom is formation of root galls (knots) and these can be seen with the naked eye. Affected roots rot.

Red spider mites (Tetranychus spp.)

Red spider mites are about 0.6 mm long. They feed on the lower leaf surface causing white or yellowish spots on the upper leaf surface. Heavy infestation results in partial defoliation.

Thrips (Megalurothrips spp. and Frankliniella schultzei)

Thrips are small (1.5 mm long), slender, brown insects with pale yellow hind wings that appear as a yellow line down the back of the body when the insect is at rest. Adult thrips have characteristic wings; the transparent wings have a fringe of hairs around the outside edge standing out in the same plane as the wing.

Several species of thrips are common on pigeon peas in Eastern Africa and are considered important pests. These thrips feed on leaves and flowers. Main damage is due to thrips feeding on flower buds and flowers. Heavy infestation can lead to shedding of buds and flowers. However, according to reports from India, pigeonpea plants produce more flowers than the plant can sustain, so many are lost naturally and it is difficult to assess thrips damage (Ikisan, 2000).

Aphids

Several species of aphids have been reported feeding on pigeon pea. The black legume aphid (Aphis craccivora) is the most common.

Bugs

Pod sucking bugs are primary pests of pigeon peas.

The most common pod-sucking bugs are: giant coreid bugs (Anoplocnemis spp), spiny brown bugs (Clavigralla spp), Riptortus bugs (Riptortus spp) and green stink bugs (Nezara viridula).

These bugs suck developing seeds through the pod wall. The seeds become shrivelled with dark patches. Attacked seeds do not germinate and are not acceptable as food. Fungal spores are sometimes transmitted with the mouthparts during feeding, resulting in rotting of the seeds. The spiny brown bug Clavigralla tomentosicollis is one of the most important pests of pigeon peas in Eastern Africa.

Sucking bug adults are difficult to control since they are very mobile and can invade crops from neighbouring sites.

Pod borers

The African bollworm (Helicoverpa armigera), the legume pod borer (Maruca vitrata = testulalis) the lima bean pod borer (Etiella zinckenella) are major pests of pigeon peas in East Africa. They feed on leaves, flowers and pods, destroying them.

The African bollworm (Helicoverpa armigera)

Caterpillars are 1.5 to 4 cm long. They bore holes on pods and feed on the seeds. Usually developing in the pods and feeding partly mature seeds.

For more information on the African bollworm click here.

The legume pod borer (Maruca vitrata)

The adult of the legume pod borer is a moth with a wing span of 15-30 mm. It has light-brown forewings with white markings and pearly white hindwings. Though mainly nocturnal, the moth may also be seen during the day. They lay eggs in the flowers or buds, or on the pods. Caterpillars are whitish with black head and rows of conspicuous brown to black spots on the dorsal, lateral, and ventral surfaces of each body segment. Fully-grown caterpillars measure about 15mm in length. They pupate in the soil. Caterpillars web leaves, flower buds and pods and feed inside the web. Flowers usually show little sign of damage until they wilt and drop. They typically attack pods at the point of contact between two pods, or between a pod and a leaf or stem.

The lima bean pod borer

Adults of the lima bean pod borer are brown moths with a wing span of about 20-25 mm. They lay eggs singly or in small groups on immature pods. Young caterpillars bore into the pod. They feed inside the pod reaching a length of 12 to 17 mm and are generally found in maturing and dried pods. Young caterpillars are green, turning red later. Faeces in the form of granules are found inside the damaging pods.

Pod fly (Melanagromyza chalcosoma)

It is a small black fly that lays eggs through the walls of developing pods. The maggots (white in colour and about 3 mm long) feed inside the green seed. The brown barrel shaped pupa is formed inside the pod but outside the seed.

There are no obvious external symptoms of attack till the fully-grown maggot chews holes in the pod walls leaving a window through which the flies emerge after pupation in the pod. Damaged seeds are of no value. The pod fly causes most damage on pigeon pea maturing during cool weather and pigeon pea planted at altitudes higher than 500 m above sea level.

Pod weevil (Apion clavipes)

It has been regarded as a major pest of pigeon pea in East Africa. Adults are small black weevils. The larvae are creamy white. Larvae damage the green seeds in pods but the damage is usually noticed only after adults emerge cutting the way out of the pod. The beetles also chew small holes in leaflets and flowers.

Blister beetles (Coryna spp. and Mylabris spp.)

Adults feed on the flowers and reduce the number of pods that are set. In location where pigeon pea is grown over large areas blister beetles cause little damage. However, in small pigeon pea plots that are in the flowering stage during the period of peak adult activity, most of the flowers may be eaten by the beetles and crop losses maybe substantial. The adults are medium to large sized beetles (2 to 5 cm in length), usually black and yellow or black and red in colour. The immature stages (larvae) do not feed on plants. They live in the soil and eat grasshopper eggs, and are therefore beneficial.

Whiteflies (Bemisia tabaci, Trialeurodes vaporariorum and Aleyrodes proletella)

Several species of whiteflies are found on cassava in Africa. Feeding causes direct damage, which may cause considerable reduction in root yield if prolonged feeding occurs. Some whiteflies cause major damage to cassava as vectors of cassava viruses. The spiralling whitefly (Aleurodicus dispersus) was reported as a new pest of cassava in West Africa in the early 90s.

The adults and nymphs of this whitefly occur in large numbers on the lower surfaces of leaves covered with large amount of white waxy material. Females lay eggs on the lower leaf surface in spiral patterns (like fingerprints) of white material secreted by the female. This whitefly sucks sap from cassava leaves. It excretes large amounts of honeydew, which supports the growth of black sooty mould on the plant, causing premature fall of older leaves.

The tobacco whitefly (Bemisia tabaci) transmits the African cassava mosaic virus one of the most important factors limiting production in Africa. The adults and nymphs of the tobacco whitefly occur on the lower surface of young leaves. They are not covered with white material. The nymphs appear as pale yellow oval specks to the naked eye.

Termites (Coptotermes formosanus)

Termites can be a serious problem for coconut palms, particularly for young trees in tree nurseries or trees that have just been transplanted into the field. Termites live in the soil in hills, construct tunnel from the hills to the palms and feed on all parts of young coconut palms. Damage occurs mainly during the dry season.

Many plants have a repellent or even insecticidal effect on termites and can be applied as spray directly against termites or as barrier around the trunk of coconut palms:

• Neem: seeds and leaves (extracts or cake)
• Quassia indica or Q. amara: bark and leaves
• Sandalwood: wood
• Chinaberry, persian lilac (Melia azedarach): bark, branches, leaves, extracts
• Euphorbia sp.: "In Tanzania, especially in Dar es Salaam and coast regions, farmers plant with each seedling 2 or 3 sticks of Euphorbia sp. to protect the young palms from termite attack. On nurseries the Euphorbia plants can be planted around the seedbed to prevent access of termites to the palm seedlings and young palms. When the palms have grown big the euphorbia is simply cut down. The practice is widespread and farmers are convinced that it really does keep termites off the susceptible seedlings ( Z. Seguni, MARI personal communication)".

Cutworms (Agrotis spp)

Cutworms cut the stem of plants below the soil surface. The damaged plant wilts and withers. First instars are 0.7-1 cm, later instars are 3.5-5 cm long.